1. Field of the Invention
The present invention relates to a working engine serving as a power source mainly for a trimmer or another portable working machine, and more particularly, to a foreign matter entanglement-preventing device, which is mounted in a working engine including a bearing mounted on an outer wall of a crankcase for carrying a crankshaft, an oil seal mounted on the outer wall of a crankcase and disposed outside and adjacent the bearing to come into close contact with an outer peripheral surface of the crankshaft, and a cooling fan attached to an outer end of the crankshaft adjacent the oil seal with its blades turned toward the crankcase, and which is adapted to prevent foreign matter such as weeds and the like from being drawn in by the cooling fan and being entangled around the crankshaft, thereby avoiding damage to the oil seal as a result of the entangled foreign matter.
2. Description of the Related Art
Such a foreign matter entanglement-preventing device in a working engine is already known, for example, as disclosed in Japanese Patent Application Laid-open No.61-25529.
In the foreign matter entanglement-preventing device disclosed in the above Japanese Patent Application Laid-open No.61-25529, a cylindrical protective tube is formed on an outer sidewall of a crankcase to surround ends of bosses of a cooling fan, while covering a crankshaft, so that the entering of foreign matter toward the crankshaft is prevented by the bosses and the protective tube. In the above structure, however, when the foreign matter has been once entangled around an outer periphery of the cylindrical protective tube, the foreign matter may be accumulated and ultimately enters into a gap between the protective tube and the bosses of the cooling fan, resulting in the occurrence of the entanglement of the foreign matter around the crankshaft.
Accordingly, it is an object of the present invention to provide a foreign matter entanglement-preventing device in a working engine, which has a simple structure and is capable of reliably preventing the entanglement of a foreign matter around a crankshaft.
To achieve the above object, according to the present invention, there is provided a foreign matter entanglement-preventing device in a working engine which includes a bearing mounted on an outer wall of a crankcase for carrying a crankshaft, an oil seal also mounted on the outer wall of the crankcase and disposed outside and adjacent the bearing to come into close contact with an outer peripheral surface of the crankshaft, and a cooling fan attached to an outer end of the crankshaft adjacent the oil seal with its blades turned toward the crankcase. The foreign matter entanglement-preventing device includes a cylindrical protective tube formed on an outer sidewall of the crankcase to cover ends of bosses of the cooling fan, while covering the crankshaft, and a foreign matter-beating piece formed on the cooling fan in proximity to an outer peripheral surface of the protective tube.
With such features, if a long piece of foreign matter such as a weed and the like, is entangled and accumulated around an outer periphery of the protective tube, the foreign matter-beating pieces rotated along with the cooling fan beat and loosen, or cut and drop the foreign matter. In this manner, the entering of the foreign matter into the protective tube can be inhibited. Therefore, it is possible to prevent the foreign matter from being entangled around the crankshaft within the protective tube, thereby avoiding damage to the oil seal as a result of the entanglement.
Moreover, the protective tube and the foreign matter-beating pieces integrally formed respectively on the crankcase and the cooling fan do not increase the number of parts of the engine and hence, the foreign matter entanglement-preventing device can be provided in a simple structure and at a low cost.